1. Field of the Invention
The present invention relates generally to optical lens driving techniques, and more particularly to an auto-focus optical lens module.
2. Description of Related Art
Taiwan Certificate No. M294046 discloses an auto-focus optical lens module, which comprises a bottom cover, two guiding pins, two conductive sheets, a lower frame, a lens sleeve, two springs, a lens, a coil, an upper frame, two magnets, and a top cover. The bottom cover is a rectangular frame body, which has four holders respectively disposed at four corners thereof for engaging with the top cover, a through hole formed at a central portion thereof so as to form an optical path for the lens, two fixing holes respectively disposed at two opposite corners of an inner surface of the bottom for the two guiding pins to be inserted. The two conductive sheets are both attached to the bottom cover but connected to two different electrodes. A central hole is formed between the two conductive sheets so as to form the optical path for the lens, the conductive sheets respectively have through holes allowing the corresponding guiding pins to pass through; the lower frame is disposed on the two conductive sheets, a central hole is disposed at the central position thereof for forming the optical path for the lens.
The lens sleeve comprises a ring-shaped frame having a central hole for assembly of the lens and two symmetrical protruding ears disposed at periphery of the frame. The two symmetrical protruding ears respectively have through holes formed therein for allowing the guide pins to pass through. The two springs are respectively disposed around the guiding pins, and bottom of the springs are respectively abutted against the protruding ears of the lens sleeve. The lens is fixingly disposed inside the central hole of the lens sleeve. The coil is disposed on the ring-shaped frame of the lens sleeve, and conductive lines at front and end portions of the coil are respectively connected to the conductive sheets.
The upper frame comprises a ring-shaped frame and two engaging bodies disposed at the periphery of the frame. By engaging the two engaging bodies with the lens sleeve, a lens sleeve group consisting of the upper frame, the coil, and the lens sleeve disposed at the periphery of the lens can be formed with the coil fixingly disposed between the ring-shaped upper frame and the corresponding ring-shaped frame of the lens sleeve. The two magnets are two symmetrical arc-shaped magnets, respectively disposed at left and right outer sides of the coil. By engaging the top cover with the bottom cover, a lens module is formed, wherein the two magnets are fixingly disposed between the top cover and the bottom frame, the two springs are respectively suppressed upward against the inner surface of the top cover and thereby disposed between the inner surface of the top cover and the protruding ears of the lens sleeve. Driven by the electromagnetic force generated by the interaction between the coil and the magnets, the lens sleeve module can be axially moved. As the two springs are respectively disposed around the guiding pins and elastically disposed between the lens sleeve module and the inner surface of the top cover, the lens sleeve module can be stably moved.
Although the above-described lens module has the function of auto-focus through the electromagnetic force, the module structure is rather complex. Also, the volume of the module structure is rather large limited by volumes of the coil and the magnets. Therefore, the abovementioned invention can only be used in conventional cameras and large-sized digital cameras, which is difficult to be applied in thin digital cameras and handheld electronic devices having camera function.
Japanese Unexamined Patent Publication No. 2003-236466, No. 2003-175364, No. 2003-112119, and No. 2004-280031 disclose various kinds of electromagnetic actuators that can be applied in different products, a common characteristic among which is a leaf spring is used to provide a suspension effect for the driven object. However, deformation range of the leaf spring limits the design solution, that is, the driving distance is limited by size of the leaf spring. In addition, the use of the leaf spring also leads to big volume of the products. With the increase of size of the leaf spring for increasing the driving distance, the volume of the whole actuator is also increased, thereby making it impossible to miniaturize the actuator. Meanwhile, spring fatigue and deformation precision of the leaf spring also adversely affect the possibility of the actuator miniaturization.
British 1 Ltd. Corporation (http://www.1limited.com) proposes a spirally rolling piezoelectric actuator using dual-chip type piezoelectric ceramics. The piezoelectric actuator has been used in cameras for driving the focus lens. The piezoelectric actuator in combination with the optical lens and the frame can be disposed in conventional cameras, digital cameras and mobile phones having camera function for auto-focus.
Although the spirally rolling actuator has advantages of small volume, big displacement, low power consumption, low noise and high compatibility, it needs a lot of labor for rolling the dual-chip type piezoelectric ceramics and connecting the circuits. Even if automatized mechanics and tools can be used to finish the work, the fabrication process is complex and difficult, which can result in low product yield and unstable quality, thereby limiting the large-scale application of the spirally rolling actuator in the industry.
U.S. Pat. Nos. 4,755,705, 4,786,836, 4,829,209, 4,935,659, 4,952,834, 4,959,580, 5,013,982, 5,708,872, 5,751,502, 5,898,526, and 5,898,528 disclose techniques related to application of ultrasonic motor (or called as piezoelectric motor) or piezoelectric actuator in conventional cameras. However, as digital cameras and lens of mobile phones having function of zoom or focus become popular, these above-mentioned ultrasonic motors or piezoelectric actuators are difficult to be received in these newly developed products.
In addition, some papers and research meetings disclose some digital cameras and camera phones with small volume piezoelectric optical lens. However, structure of the piezoelectric optical lens is rather complex and related components must be separately fabricated instead of being fabricated in batch-type. Meanwhile, the assembly of the piezoelectric optical lens, particular assembly of the piezoelectric stator, is quite difficult, which decreases the driving force for simple piezoelectric optical lens. Particularly, assembly of tiny components needs a lot of labor because they cannot be assembled by automatized machine, thereby increasing the labor and fabrication cost. Therefore, although the piezoelectric optical lens has advantage of small volume, the cost of it is rather high, which adversely affects the application of the piezoelectric optical lens in the industry.
Therefore, there is a need to provide a piezoelectric optical lens to solve the above problems.